Method for producing security marks and security marks

ABSTRACT

The invention concerns a method for producing security marks on a support having a first face and a second face opposite said first face which consists in the following steps: high resolution printing with a varnish on the support first face; treating the support by electrolysis; washing and drying the support.

CROSS REFERENCE TO RELATED APPLICATION

The present application is the U.S. national stage application ofInternational Application PCT/EP00/07322, filed Jul. 28, 2000, whichinternational application was International Application claims priorityof Luxembourg Patent Application 90424, filed Jul. 30, 1999.

This is a 371 of PCT/EP00/7322 filed Jul. 28, 2000 which claims priorityof Luxembourg Patent Application 90424, filed Jul. 30, 1999.

This invention concerns a manufacturing process for security marks toprotect products and also security marks.

STATE OF THE ART

The development of reprographic techniques is making it increasinglyeasy to copy or forge documents, in particular fiduciary papers,banknotes, stamps, etc.

In order to verify the authenticity of a product, the identifyingelements carried by the product are checked. Such identifying elementsgenerally comprise marks integrated within the product that can only beread by a detector. Verification involves comparing the type, shape andpositioning of the identifying elements with specimen identifyingelements inaccessibly and/or inviolably stored in a memory inside theverifying device. This is the procedure with products such as banknotes.Such products comprise marks and check elements that are integratedwithin the notes and can generally be read with the aid of luminousradiation of a specific wavelength, preferably in the non-visible lightrange.

However, improvements in means of analysis available on the market aremaking it more and more difficult to take effective countermeasures,that is to say, means of preventing unauthorised persons from detectingand analysing the marks and identifying elements and subsequently usingthat knowledge to forge products by incorporating identifying elementswhich, when read by a detector, are interpreted by the detector asgenuine identifying elements.

In the field of security of identification, it is certainly possible, bydeploying sophisticated means, to make an object or product hard toforge or, at least, to make forgery sufficiently difficult to be nolonger cost-effective.

The same cannot be said of products that are manufactured or used invery large numbers, such as banknotes or fiduciary papers, for instance:in this case, the cost of manufacture and in particular the cost of thesecurity devices must be kept within limits. In other words, in the caseof such products, the security devices or anti-forgery devices must besuitable for integration into an industrial process and must becompatible with industrial conditions of implementation. Themanufacturing cost involved must be reasonable.

At present, therefore, banknotes, fiduciary papers, stamps, etc. areprinted by conventional printing techniques offering limited scope forprecision printing and positioning of identifying elements.

The integration of identifying elements in the form of holograms issubject to the same physical limits of error and thus does not offer thenecessary security.

OBJECT OF THE INVENTION

The object of this invention is to present a process by which productscan be made considerably more secure against forgery.

GENERAL DESCRIPTION OF THE INVENTION CLAIMED, INCLUDING THE MAINADVANTAGES

According to the invention, this aim is achieved by a manufacturingprocess for security marks on a medium having a first surface and asecond surface opposite said first surface comprising the followingstages:

-   -   high-resolution printing of a varnish on the first surface of        the medium;    -   treatment of the medium by electrolysis;    -   washing and drying of the medium.

High-resolution printing makes for high precision in the making andpositioning of the security marks. A genuine product, that is, one whichcarries an authentic mark, can be recognized with a security which isincreased by several orders of magnitude.

The mark can be used as it is, or it may be transferred to the surfaceand/or into the core of the material to make it more secure and forauthentication purposes.

The precision with which the mark is made also allows a more complexshape, i.e. the outline, the inclusions and resists, or more complexplacing of the identifying elements and, above all, it enablesidentifying elements to be integrated that are only detectable orperceptible in conditions compatible with the precision of manufacture.

Before printing, the medium is preferably coated on the first surface.The coating preferably comprises one or more metals, one or more oxides,one or more metallic salts or metalloids or a mixture of these.

Between the coating and the varnish, an intermediate separating layerand/or an intermediate relief layer can be deposited. The latteradvantageously facilitates the creation of micro-reliefs by stamping.The intermediate layers form protective layers for the security mark andgive it abrasion resistance and rubbing resistance, for example.

The intermediate layer is able to carry, while ensuring good adhesion,another intermediate layer, achieving transparency that does not impairthe final appearance of the mark.

The intermediate layer advantageously comprises variable diffractingoptical motifs and/or holograms.

High-resolution printing is preferably carried out using an electricallyinsulating varnish.

The varnish advantageously comprises a polymer, preferably of thecellulose and/or metal and/or plastic and/or vacuum metallized plastictype.

The polymer for example comprises a mixture of nitrocellulose resins,preferably nitroalcohols, with the addition of resins to improve varnishresistance to subsequent treatments, such as gum arabic and rosin, etc.The polymer can also comprise a mixture of resins with the addition ofone or more adhesion promoters, preferably butyl acetate tartaniate.

Alternatively, the varnish is insoluble and comprises nitrocellulosepolymers comprising a charge which varies according to the subsequentfunction of the mark, in particular conductive or insulating pigments orcharges such as metal oxides, preferably oxides of titanium, iron,boron, nickel, chromium, carbon, silica, etc. used in pure form or in amixture.

The varnish is advantageously deposited by any printing process that candeposit varnish with great precision and high resolution.

In a preferred embodiment, the varnish is deposited by means ofphotogravure printing.

Photogravure allows high-resolution printing without indentation. Theprecision of printing thus allows the precision of detection to beenhanced in a way that is not suspected and, on the other hand, allowsincreased precision or reduction in size of the identifying elementswhereas, hitherto, said precision was considerably limited by the riskof error associated with lack of manufacturing precision. Said precisionallows multiple identifying elements to be camouflaged more readily;these are imperceptible in normal conditions of analysis, because theyare not to be suspected, and they lie a good way beyond the limits oferror currently conceivable. Finally, said very high precision makes itpossible to increase the number of mark elements and increase securityagainst forgery commensurately.

The varnish deposited on the base deposit is advantageously treated soas to modify its pattern, either by addition of material or by ablation.Material may be added by any printing process preferably using ink jetdevices. Ablation can be performed by any means of localised destructionpreferably by laser etching by a beam passing through a screencomprising windows or by a brush which is guided to draw lettering orgraphics which can be variable with no contact with the metal film. Inthis way, constant and/or variable motifs can be included in thevarnish, such as numbering, indexing, customisation, etc.

In another preferred embodiment, the varnish is deposited by means ofdigital printing. Digital printing possibilities include those whicheffect printing by applying ink or a coating, such as ink jet printing,liquid, solid or dry toner printing, elcography, with or without contactwith the base deposit. The use of digital printing allows smallproduction runs to be manufactured and enables designs that vary partlyto be produced, such as numbering for instance. Moreover, digitalprinting avoids some of the drawbacks of photogravure printing, such asthe making of an expensive printing form, which in some cases causes along manufacturing lead-time. Digital printing is thus simpler, fasterand cheaper than photogravure printing, while nonetheless retaining highresolution.

In an advantageous embodiment, the varnish contains a charge. Thischarge can for example contain a marker. Said marker can comprisemicro-globules, preferably under 1 μm in size. Being so small, themicro-globules are undetectable to the naked eye. However, they aredetectable by microscope in a narrow pass-band light, for examplefluorescent in UVA lighting.

Stable trace elements, such as a DNA chain, are advantageouslyincorporated with the micro-globules. Said molecules are preferablycoated with a protective polymer.

By using such DNA chains, a marker is obtained which is invisible to thenaked eye with more than 10¹⁸ possible unique codes.

The marker from the security mark is compared for identification withthat in a DNA database held by a trustworthy third party.

The outer surface of the micro-globules is preferably covered withfluorescent and/or phosphorescent pigment particles. Said pigmentparticles turn the micro-globules visible when examined under themicroscope in light with a pass-band corresponding to the fluorescenceor phosphorescence of said pigments.

Etching of the coating is preferably carried out by electrolysis betweenthe coating and an anode. The anode is for example an insoluble titaniumanode, comprising a folded sheet, immersed in an aqueous electrolyte.The aqueous electrolyte advantageously comprises a mineral acid and itssalt or a mineral base and its salt, preferably NaOH+NACI concentrated10% by weight.

By using a soluble electrode, electrolysis also makes it possible toapply a deposit to the varnish. In order, for instance, to deposit alayer of copper on the varnish, the anode can be a copper anode and theaqueous electrolyte can comprise CuSO₄ and H₂SO₄.

In a preferred embodiment, the security mark is glued by the surfacecomprising the varnish onto a final substrate, after first etching thecoating. Then, the medium, the intermediate layers and the coating canbe removed so that only the varnish appears on the final substrate. If aseparating film is included, it suffices to separate the separating filmfrom the final substrate and the varnish appears. In the case of anadhesive mark, it suffices to detach the film from the medium for thecoating to be pulled off by the medium to reveal the varnish. In thecase of a patch or strap deposited by a hot transfer method, scratchingthe covering reveals the coating.

The invention also concerns a facility for the manufacture of securitymarks comprising a feed station supplying a medium with a coatingapplied, a printing station where varnish is applied to the medium,discharging to an electrolysis station where the medium is etched, awashing plant to clean the surface of the medium, a drying station, aninspection station and a winding station.

In a preferred embodiment, the printing station is a photogravureprinting station. By means of a photogravure window, the photogravureprinting station enables a motif to be printed on a web with very greatprecision.

In another preferred embodiment, the printing station is a digitalprinting station. Said station also enables a motif to be printed withvery great precision, though preparation of a window is not necessary,with the result that printing is faster and cheaper.

The facility comprises an electrolysis station at which are arrangedinsoluble electrodes immersed in a live electrolyte permitting rapidcorrosion of the unprinted areas of a pre-printed metal or metallizedfilm that kisses the surface of the electrolyte as it passes.

The aqueous solution preferably comprises a salt with its base orassociated acid such as NaOH and NaCl in a concentration between 5 and150 g/l, preferably 100 g/l.

The electrolyte temperature is advantageously between 5 and 80° C. andis preferably 40° C.

The potential difference between the electrodes is DC, between 2 V and21 V, and is preferably 6 V.

At the electrolysis station, the electrode is a bar of triangular shapehaving one of the angles of the triangle pointing at the film. Thisgeometry is favourable to the concentration of current flows towards themetal film to be corroded.

The electrode material is a material which is insoluble in the aqueousdeveloping solution, even in the presence of an electric current, suchas titanium.

According to another characteristic, the facility comprises a set ofmachines and equipment comprising a treatment zone with solubleelectrodes immersed in a live electrolyte for rapid deposit on to a filmpre-printed with windows.

In this facility, the developing solution is an electrolyte comprising asalt with its base or associated acid such as CuCl₂ and HCl in aconcentration between 5 and 150 g/l and preferably 100 g/l.

It is also advantageous for the current across the electrode terminalsto be a direct current applied at a voltage between 5 and 30 V,preferably 6 V.

According to an advantageous characteristic, the electrode bar sectionhas a geometry favourable to dissolution of the electrode metal, thus amaximum area in contact with the electrolyte, for example a circularsection.

In this case, the electrode material is a material soluble in theelectrolyte, such as copper in order to deposit a copper film.

Advantageously, the anodes and cathodes are immersed in parallel,separated from one another by isolating partitions, perpendicular to thefilm path, in the window developing solution, at a distance of a fewmillimeters from the film, preferably 1 mm at most, which kisses thesurface of the electrolyte but is not immersed in it.

According to an embodiment of the invention, the electrode bar sectionhas a geometry favourable to concentration of current flows towards themetal film to be corroded and favourable to its dissolution in theelectrolyte, preferably having a drop shape with the point of the droppointing towards the film.

In a preferred embodiment, the electrolysis station comprises anelectrolysis tank with partitions. This allows a succession of solubleand insoluble anodes to be used in the electrolysis tank with suitableelectrolytes. In this way, the medium can be successively etched thencovered with a deposit localised on the varnish. The result obtained ismulti-layers which are marked on the printed varnish.

The facility can comprise a set of machines and equipment comprising awashing zone with drying taking place between steel rollers and polymerrollers to limit carry-over and facilitate drying by evaporation of thewashing liquid, such that the soluble varnish is dissolved and thetreated film is dry and has no traces of electrolyte incompatible withits subsequent use.

Advantageously, the facility comprises a set of machines and equipmentarranged in series so as to comprise one machine with several separatestations, to keep printing separate from the other operations which are,in turn, grouped together on a second machine.

Preferably, the facility comprises a set of machines and equipmentcomprising two inspection zones between printing and treatment and athird inspection zone after drying, fitted with sensors for continuousdetection of the conductivity of the different zones and video camerasto monitor the resolution standard at the different stages ofoperations.

The invention also concerns a security mark comprising a medium madefrom a material which is transparent in visible light, a coating appliedto one surface of the medium and a varnish covering at least part of thecoated surface of the medium, the varnish being applied to the medium ina motif which is invisible to the naked eye.

The medium is preferably a polymer film such as a polyester film. Thispolymer film advantageously has special characteristics compatible withthe use of the end-product, such as tear resistance and temperatureresistance properties allowing it to be used in hot transfer printing.The film used will preferably be bi-oriented polyester between 16 and100 μm thick, preferably between 16 and 23 μm.

The polymer medium film preferably has characteristics compatible withthe use of the end-product, such as appropriate tear resistance whenwire cut and suitable density for use in making films partly orcompletely immersed in the paper.

The polymer medium film has, if applicable, characteristics that make itsuitable for the use of the end-product, such as capability oflamination, hence wetability or surface tension capability, between 37and 55 DIN, preferably 42 DIN, for the making of separating film.

The coating preferably comprises one or more metals, one or more metaloxides, one or more metalloids, and/or mixtures of these obtained byvacuum sublimation.

Between the coating and the varnish is advantageously deposited one ormore intermediate layers. Such intermediate layer can, for instance, bean intermediate separating layer preferably made of polymer wax, therole of which is to break when detached from the subsequent layers andfrom the medium. The intermediate layer can also be an intermediaterelief layer comprising a varnish made of polymer, preferablypolyurethane, the role of which is to protect the final layer and or tobe hot-stampable and pressure-stampable. Stamping enables micro-reliefsto be created that constitute variable diffracting optical motifs and/orholographic motifs.

The coating can be comprised of several layers, namely a firstseparating layer, a second layer to protect the next layer and a thirdlayer, of one or metals, one or more metal oxides, one or moremetalloids or a mixture of these which is vacuum-deposited, which hasbeen treated, printed with a varnish, charged with at least one marker,laser etched and/or modified by digital printing, treated byelectrolysis, coated with a bonding layer, a second layer comprised of acatalytic varnish and a third layer, comprised of one or moreheat-fusible polymers to create a material which is suitable, aftercutting and winding, for hot transfer printing to make secure fiduciarydocuments and other papers such as passports, identity cards, drivinglicences, registration plates, banknotes, cheques and packaging.

The varnish is advantageously a varnished charged with a marker in theform of micro-globules comprising a DNA chain. To the micro-globules canbe attached fluorophores the presence of which can be verified with theaid of a microscope comprising a light source with a wavelength between3,000 and 4,000 Å, fitted with a filter.

The coating polymer comprising the micro-globules forms an entity whichis resistant not only to the printing environment but also toenvironments where the marked product is to be used.

The DNA molecules are preferably synthesized to constitute a unique codethat can be recognized after chain amplification by comparison to thatstored in a database held by a trustworthy third party.

DESCRIPTION WITH REFERENCE TO THE FIGURES

Other special features and characteristics of the invention will becomeclear from the detailed description of some advantageous embodimentsgiven below, by way of illustration, with reference to the attacheddrawings. These show:

FIG. 1: Sectional view of a film during the different stages (A, B andC) of production (coated medium, varnish, electrolytic etching)

FIG. 2: Sectional view of a film during the different stages (A, B, Cand D) of production (coated medium, varnish, laser etching,electrolytic etching)

FIG. 3: Sectional view of a film during the different stages (A, B, C, Dand E) of production (coated medium, varnish, electrolytic etching,gluing, removal of layers)

FIG. 4: Micro-globules

FIG. 5: General arrangement of a machine for carrying out of the process

FIG. 6: Schematic view of a photogravure printing assembly

FIG. 7: Top view of photogravure printing assembly

FIG. 8: Desired shape of an imprint

FIG. 9: Photogravure window (etched area with continuity line in contactwith the etched cells)

FIG. 10: Photogravure window (etched area with continuity line not incontact with the etched cells)

FIG. 11: Printed result

FIG. 12: Schematic view of a film physico-chemical treatment assembly

FIG. 13: Top view of film physico-chemical treatment assembly

FIG. 14: Perspective view of film physico-chemical treatment assembly

FIG. 15: Hybridisation of the DNA sample with its twin from the database

On the figures, the same reference numbers denote identical or similarelements.

FIG. 1A shows a sectional view through a film medium 10 coated with anintermediate layer 12 and a metal layer 14. Holograms 16, 18 areintegrated into the intermediate layer 12. On the metal layer is printed(FIG. 1B) a discontinuous layer 20 of varnish. In FIG. 1C, the metallayer has been removed by electrolysis at the places where varnish hasnot been applied.

FIG. 2A shows a sectional view through a film medium 10 coated with anintermediate layer 12 containing holograms 16, 18 and a metal layer 14,on which—in FIG. 2B—is printed a layer 20 of varnish. One of theholograms 18 constitutes a spot which can be used to check filmunwinding. The varnish is printed everywhere on the film except for thespots 18. It is then laser etched (FIG. 2C) to partly destroy thevarnish and thus modify the print motif. In FIG. 2D, the metal layer hasbeen removed by electrolysis in those places where varnish has not beenapplied or where the varnish has been removed by laser etching,respectively.

FIG. 3A shows a section through a film medium 10 coated with anintermediate layer 12 and a metal layer 14, on which—in FIG. 3B—isprinted a discontinuous layer 20 of varnish. The varnish containsmicro-globules 22 (FIG. 4) under one micron in size, to which havepreviously been attached stable trace elements so as to constitute acoded DNA chain. The film is then etched (FIG. 3C) so as to remove themetal layer 14 at those places not protected by the varnish 20. Glue 24is used to attach a final substrate 26 to the varnish 20 (FIG. 3D)before removing—FIG. 3E—the surface layers over the coating to revealthe latter.

FIG. 5 shows a facility for carrying out of the process described above.This facility comprises a feed station A to which is delivered the filmwith its base deposit BA1, wound on a reel. At this feed station, thereel is unwound to feed a printing station B; then, on leaving theprinting station, the web BA2 enters an electrolysis station C wherephysico-chemical treatment is carried out on the windows in the filmBA3. This electrolysis station C is followed by a washing station D,where any water-soluble varnish is removed, producing the film BA4, andthe web is rinsed. The web BA4 then enters a drying station E and,finally, an inspection station F from where it is fed to the winder G.

The feed station A comprises an unwinder A1 carrying the reel A2. Thisunwinder is driven by a motor controlled by a feeding system A3, whichcontrols the tension of the web BA1. The web then enters the printingstation B which, in this example, is a photogravure printing station,comprising a printing assembly (FIGS. 6 and 7) with an ink fountain B1,a gravure cylinder B2 dipping into the ink fountain B1 to cover thesurface comprising photogravure cells and the window outline. Thiscylinder is co-operative with a scraper B3 which removes the surface inkso as to leave only the ink inside the cells or etching. The inkfountain B1 is supplied from a tank B4 containing the coating product bymeans of a pump B5 and a pipe B6. The tank B4 is fitted with a viscositydetector B6, such as a viscometer, to enable the viscosity of thecoating liquid to be controlled.

This photogravure assembly B can be fitted with a system for reading aspot, or marker detectable by a photoelectric cell, arranged on themetallized web and enabling the web to be controlled such that thepositioning of the printing window is in register with the motifs on themetallized web comprising graphics which may be pre-printed.

The liquid level in the ink fountain B1 is controlled by means of anoverflow B7 which flows back into the tank B4, such that the gravurecylinder B2 is always immersed to the same depth in the ink fountain B1.

The cylinder B2 is co-operative with a press roller B10 positioned abovethe web BA1, cylinder B2 being underneath the web.

The web BA1 consists schematically, as shown in FIG. 1, of a plasticmedium 10 and a base deposit 14, such as a metal.

Turning in the direction of the arrows, the gravure cylinder B2compresses, with the press roller B10, the web BA1 and deposits imprintsof varnish corresponding to the windows or print areas or coatings Icorresponding to the windows.

FIG. 7 is a top view of the photogravure printing assembly shown in FIG.6. This figure shows the gravure cylinder B2, the press roller B10 withan arrow indicating compression and the web BA in top view. The gravurecylinder B2 has a surface which is etched according to a photogravurewindow or print area B21 of relatively complex shape, which effectsprinting I of the varnish on the base deposit 14 on the web BA1 (whichthen becomes web BA2).

FIGS. 8–11 show more explicitly the construction of the etched surfaceof the photogravure window.

FIG. 8 shows the desired outline of the photogravure window, that is tosay, the outline of the future graphic (I100).

Starting with this shape I100, the surface of the photogravure window isetched in the cylinder. This window comprises an etched surface havingtroughs or cells K100, separated by walls K101, the whole beingsurrounded by a fillet K102, which edges the troughs and the spacesbetween the troughs K100.

In this figure, the cells are represented by black squares with roundedcorners, possibly truncated, separated by walls (partitions, also calledbridges) K101, which are white.

The set of cells or troughs is surrounded here by a fillet, that is tosay, a very narrow groove which fills with ink but which confines thespreading of the ink from the cells to give the printed image acontinuous, precise outline, precisely delimiting the window limit in apredetermined manner.

In FIG. 9, this fillet K102 runs over and abuts the troughs or isadjacent to them.

In the case of FIG. 10, the window 1200 also comprises cells K200separated by walls K201 and the whole is surrounded by a fillet K202which is farther from the edge of the cells K200 (truncated or not) thanin the embodiment according to FIG. 9.

The fineness of the line comprising the fillet depends on the resolutionof the scriber drawing the window or windows; thus, the choice ofgravure forms in FIGS. 9 and 10 also determines the viscosity of theprinting liquid. As stated, once dried this liquid is passivated, thatis to say, inert with respect to the physico-chemical action to beperformed.

Lastly, FIG. 11 shows the printed image I300 with its very preciseoutline which is not indented.

Returning to FIG. 5, the electrolysis station C comprises anelectrolysis tank C1 which is kissed by the web BA2, after printing atthe printing station B. This electrolysis station also comprises a hoodC2 to extract the electrolysis gases. Details of station C2 are shown inFIGS. 12, 13 and 14.

The schematic side view in FIG. 12 of the electrolysis station C showsalternating electrolysis tanks C3, C4, C5 and C6 connected by pipes C7and a feed pump C8 to an electrolyte tank C9. In fact the web BA2,coated with the coatings I, touches the surface of the liquid inelectrolysis tanks C3–C6. Each of these tanks houses an electrode C10,C11, C12 and C13 of opposite polarity and electrolysis takes place fromone tank to another.

At the exit there is a collecting hopper C15 which collects the liquiddripping from the web BA3 squeezed out as it passes between two rollersC16, C17. The drained liquid is collected in the hopper C15 beforereturn to the tank C9.

FIG. 13 shows a top view of the electrolysis assembly C1, showing inparticular the partitions C20, C21 and C22 between the tanks. Thisfigure also shows how the positive and negative electrodes are connectedto a common collector rail C30, C31.

FIG. 14 shows a perspective view of the arrangement of the electrolysisassembly C1. The same reference numbers as above have been used, but thedescription will not be repeated.

The conditions in which electrolysis takes place depend on the type ofmetal to undergo electrolysis. The electrodes are non-consumableelectrodes, which simply remove the metallisation from the film at theplaces not protected by the passivation layer, in other words, outsidethe window outlines.

The situation is different if the aim of electrolysis is to deposit orremove and deposit a metallising layer, as mentioned above.

Finally, the window printing and electrolysis operations can be repeatedwith different window shapes, one on top of another, for example inorder to form an integrated circuit. In this case there will be asuccession of stations B, C and possibly D, alternately.

Next, the web BA3 enters the washing station D. At the washing station,the web BA3 is rinsed in order to remove electrolyte residues anddissolve the covering layer, in particular the passivation layer. Thiswashing station D comprises various return cylinders D1 and D2 whichtake the web BA3 to a first tank D4 and then into a second tank D5.These tanks contain a liquid to rinse the electrolyte and/or solvent andcoating. The detailed structure of these rinsing tanks will not bepresented. This is a set of rollers defining a route for the web throughthe washing bath.

The washing process incorporates drying between steel rollers andpolymer rollers to limit carry-over and facilitate drying by evaporationof the washing liquid, such that the film is dry and has no traces ofelectrolyte incompatible with its subsequent use.

Downstream from the washing station D, the web BA4 enters the dryingstation E which is fitted with means of ventilation and air extractionE1, E2, E3, E4 and, finally the dried web BA5 enters an inspectionstation F, which is equipped with a video camera F1 which views an areaof the film BA5 for the purpose of manufacturing quality control. Saidinspection is supplemented by a measurement of optical density andresistivity (not shown). These inspections are performed continuously.On leaving the inspection station F, the film is wound at a windingstation G. The winding station is similar in structure to the unwinderA, but works the opposite way round. It comprises an arm G1 which isfitted with a motor and forms the roll G2.

After inspection of the web, the web is fed and wound with tensioncontrol to prevent deformation due to the overthick areas.

The web is guided through the facility shown in FIG. 5 in synchronisedmanner, with the aid of reference marks and readers and also controlcircuits. Said devices are not shown.

The facility has the advantage of a treatment speed capable of exceeding250 m/min. The treatment is not sensitive to the presence of metaloxides protecting the metallized surface of the film. This is a notableadvantage over the previous chemical process. The possibility ofdepositing a metal layer of a different type to that which has beencorroded allows metal multi-layers to be manufactured.

The resolution of the metallized line that is produced is the printingresolution, because the thickness of the corrosion mask can be 2 micronsor less.

Lastly, to facilitate manufacturing operations, the corrosion resist canbe printed on a separate machine from the treatment machine.

To establish the nature of the DNA code contained in the micro-globules,a comparison is made with codes stored in a database, searching for thetwin that will identify the origin of the product.

The micro-globules are visible in suitable lighting with the aid of aweaver's glass or a lens with magnification greater than 12.

Taking a sample of a few fragments of varnish, approximately 10micro-globules, is sufficient for the purpose of laboratory analysis inorder, after purification and concentration using a column and membrane,to compare the sample DNA code with the DNA reference code database inorder to determine the sample code and establish the user of the codecorresponding to the sample code, using a DNA amplifier.

After a series of 40 thermal cycles (30–90° C.), hybridisation of theDNA sample with its twin from the database is sought. The two curvesattached show, in FIG. 15A an example of hybridisation and in FIG. 15Bthe absence of hybridisation, hence correspondence between the sampleDNA and that in the database.

In analysis (A), the sample DNA has found its twin and the sample DNAcode corresponds to the database DNA code.

1. Security mark comprising the following layers: a medium made of amaterial which is transparent in visible light; a coating applied to onesurface of the medium, said coating forming a coated area; and a varnishcovering at least part of the coated area of the medium where thevarnish is arranged on the medium in a pattern which is invisible to thenaked eye; wherein the varnish is a charged varnish; wherein the varnishis a varnish charged with a marker; wherein the marker is a marker inthe form of micro-globules.
 2. Mark as claimed in claim 1, wherein themedium is a polyester film.
 3. Mark as claimed in claim 1, wherein thecoating comprises one or more metals.
 4. Mark as claimed in claim 1,wherein between the coating and the varnish is one or more intermediatelayers.
 5. Mark as claimed in claim 1, wherein the micro-globulescomprise a DNA chain.
 6. Mark as claimed in claim 1, whereinfluorophores are attached to the micro-globules.
 7. Mark as claimed inclaim 1, wherein the mark is integrated into a product or object inorder to make it difficult to forge.
 8. A security mark comprising thefollowing layers: a medium made of a material which is transparent invisible light; a coating applied to one surface of the medium, saidcoating forming a coated area; and a varnish covering at least part ofthe coated area of the medium where the varnish is arranged on themedium in a motif which is invisible to the naked eye; wherein thevarnish is a charged varnish; wherein the varnish is a varnish chargedwith a marker; wherein the marker is a marker in the form ofmicro-globules.
 9. Mark as claimed in claim 8, wherein themicro-globules comprise a DNA chain.
 10. Mark as claimed in claim 8,wherein fluorophores are attached to the micro-globules.
 11. Mark asclaimed in claim 8, wherein the medium is a polyester film.
 12. mark asclaimed in claim 8, wherein the coating comprises one or more metals.13. Mark as claimed in claim 8, wherein between the coating and thevarnish is one or more intermediate layers.
 14. Mark as claimed in claim8, where the coating comprises one or more oxides.
 15. Mark as claimedin claim 8, wherein the coating comprises one or more metallic salts.16. Mark as claimed in claim 8, wherein the coating comprises one ormore metalloids.
 17. Security mark comprising the following layers: amedium made of a material which is transparent in visible light; acoating applied to one surface of the medium, said coating forming acoated area; and a varnish covering at least part of the coated area ofthe medium where the varnish is arranged on the medium in a patternwhich is invisible to the naked eye; wherein the coating comprises oneor more oxides.
 18. Security mark comprising the following layers: amedium made of a material which is transparent in visible light; acoating applied to one surface of the medium, said coating forming acoated area; and a varnish covering at least part of the coated area ofthe medium where the varnish is arranged on the medium in a patternwhich is invisible to the naked eye; wherein the coating comprises oneor more metallic salts.
 19. Security mark comprising the followinglayers: a medium made of a material which is transparent in visiblelight; a coating applied to one surface of the medium, said coatingforming a coated area; and a varnish covering at least part of thecoated area of the medium where the varnish is arranged on the medium ina pattern which is invisible to the naked eye; wherein the coatingcomprises one or more metalloids.